The present invention relates to the use of N-([1,2,4]-triazolopyrimidin-2-yl)sulfilimine compounds as catalysts in the reaction of aromatic sulfonyl chloride compounds with N-([1,2,4]triazolopyrimidin-2-yl)amines to form N-([1,2,4]triazolopyrimidin-2-yl)aryl sulfonamide compounds.
More particularly, the present invention concerns an improved process in which 3-picoline or 3,5-lutidine is used as the base in the sulfilimine catalyzed coupling.
Recently, a series of N-([1,2,4]triazolopyrimidin-2-yl)aryl sulfonamides have been found to be valuable herbicides; see, for example, U.S. Pat. Nos. 5,858,924; 6,518,222; and 6,559,101. The preparation of triazolopyrimidine sulfonamides in general and N-([1,2,4]triazolopyrimidin-2-yl)aryl sulfonamides in particular by the reaction of aromatic sulfonyl chloride compounds with N-([1,2,4]triazolopyrimidin-2-yl)amine compounds typically gives unsatisfactory results because the reaction is slow and the yields are poor and susceptible to impurities in the raw materials. U.S. Pat. No. 5,177,206 teaches that a mixture of a pyridine base and dimethyl sulfoxide gave improved coupling results in many instances. U.S. Pat. No. 5,973,148 teaches that sulfilimines in the presence of an aromatic tertiary amine base also facilitate this coupling in certain cases. Nevertheless, the preparation of N-([1,2,4]triazolopyrimidin-2-yl)aryl sulfonamides wherein the aromatic sulfonyl chloride compound possesses one or, especially, two ortho-substituents is often particularly unsatisfactory because of the steric deactivation effect and, when the substituents are electron-rich, the electronic deactivation effect of ortho-substituents. Even though aromatic nitrogen heterocycles have long been known to catalyze the reaction of many sulfonyl chloride compounds with amines to form sulfonamides, methods of obtaining N-([1,2,4]triazolopyrimidin-2-yl)aryl sulfonamides more readily and in improved yields are desirable.